Metallic wires are widely used in medical procedures, a common example being the guidewires used to locate intravascular devices such as angioplasty catheters. For various reasons, it is often desirable to join two discrete wire elements. For example, using different metal alloys can impart distinct handling characteristics to each wire element. By varying properties such as elasticity, strength and torqueability in each wire element, the overall handling of the guidewire can be varied or improved.
Conventional means for joining discrete wire elements involves the use of a third component, such as a hypotube. One end of each wire element is plunge ground and then inserted into the joining hypotube. The wire elements then can be secured to the hypotube, and thus to each other, by soldering or gluing. These prior art methods can be improved upon because the hypotube itself is expensive and increases manufacturing time due to the handling required to glue each wire element into the hypotube.
Accordingly, there is a need for improved wire joining processes that allow discrete wire elements to be joined without the use of a third element. There is also a need for wire joining processes that facilitate manufacturing and decrease costs. Additionally, it would be desirable to have a wire joining technique that produces a joint with a smooth continuous outer surface at the joint.
The invention is directed to a process for forming a small diameter elongated device for use in a medical procedure, such as a guidewire, by joining a first elongated member to a second elongated member by forming a male end at an extremity formed of a first continuous material of the first elongated member, forming a female end at an extremity formed of a second continuous material of a second elongated member, inserting the male end into the female end, and permanently securing the male end to the female end. In one embodiment, formation of the female end is achieved by forming a hole by electrical discharge machining. In another embodiment, formation of the female end consists of forming a hole by laser drilling. Other focused energy methods are also suitable for forming the female end. Forming the male end can be carried out by mechanical abrasion, such as plunge grinding. Friction filting, crimping, soldering, gluing, brazing, laser welding, combinations thereof, or other suitable means may also be used to permanently secure the male end within the female end.
The invention is also directed to an elongated device for performing a medical procedure with a first elongated member having a male end at an extremity formed of a first continuous material permanently secured within a female end at an extremity of a second elongated member, the extremity of the second elongated member being formed of a second continuous material. The male and female ends being formable by the methods discussed above. In one embodiment, one elongated member is formed from stainless steel while the other elongated member is formed from a shape memory material such as Nitinol. In other embodiments, any suitable biocompatible material may be used for the elongate members or extremities thereof, including other metals, polymeric compositions or composites.